A drug is any chemical we take for a specific therapeutic action. But just how exactly do these chemicals cause these actions? Generally speaking, each drug has one target within the human body that it interacts with - this interaction between the drug and its target is what causes the therapeutic effects. So what are the things the drugs are working with? For over 90% of drugs, their targets are proteins within the body.
When the word protein comes up, most people think of it in the context of nutrition. In nutrition, protein is a class of nutrients the body needs to intake in order to build muscle, maintain the immune system, and function properly. When you are eating nutritional protein, what you are eating on an atomic scale is millions and millions of individual protein molecules (a molecule is anything that is made up of more than one atom like water or a drug). These protein molecules perform chemical reactions that allow our bodies to execute actions. For example, networks of proteins are responsible for sight, hearing, digestion, and all thoughts. When you snap your fingers, millions of proteins perform synchronized chemical reactions to allow you to do this! In fact, any time you do anything your body's proteins are busy at work. These proteins are all very different from each other; each one is designed with a specific "job" to do. Drugs interact with the proteins and preventing or changing how the proteins do their "job" is how drugs work
Now there are two main types of protein molecules that drugs target called receptors and enzymes.
Receptors are proteins that can be turned on or off by a drug. You've probably heard of the serotonin receptors or dopamine receptors in the brain - these are receptors that are turned on by serotonin or dopamine, respectively. When a drug interacts with a receptor, it can turn it on or off. The receptor then tells the rest of the cell what to do. An example of a drug that targets a receptor is morphine. Morphine turns on the opioid receptor which then leads to decreased pain.
Enzymes are proteins that perform chemical reactions. They usually are involved in either making something or breaking it apart. A drug typically will turn off an enzyme and prevent it from making its product. An example of a drug that targets an enzyme is Advil. Advil (ibuprofen) turns off the enzyme called COX (cyclo-oxegenase) which leads to reduced inflammation and reduced pain.
My entire dissertation was on one enzyme specifically in the endocannabinoid system. I'll be posting a lot about the specific drug targets that have been evaluated in the ECS later!
That's it for now - if you have any questions related to drug targets, feel free to ask!